Frustration with iBook--no connection after waking

This really is getting frustrating having to type a command (sudo ifconfig en0 down ; sudo ifconfig en0 up) into Terminal to reestablish my cable connection every time I wake my iBook from sleep.

Might be a little easier to make an Applescript and run it from the Script Menu:

Do shell script "sudo ifconfig en0 down ; sudo ifconfig en0 up"

Anyone have a clue what's going on? Did something get corrupted? How can I fix this?

I don't know, when I updated the same thing happened to both Airport machines. Suddenly neither would connect to a network on waking. For Airport, there's a prefpanel item to "Join a certain network" which had to be selected.
However, there's no such item for ethernet.